[PATCH v2] dma-buf: fix an error pointer vs NULL bug

[Sumit Semwal]

On Thu, 6 Jul 2023 at 18:24, Christian König <christian.koenig at amd.com> wrote:
>
> Am 06.07.23 um 14:37 schrieb Dan Carpenter:
> > Smatch detected potential error pointer dereference.
> >
> >      drivers/gpu/drm/drm_syncobj.c:888 drm_syncobj_transfer_to_timeline()
> >      error: 'fence' dereferencing possible ERR_PTR()
> >
> > The error pointer comes from dma_fence_allocate_private_stub().  One
> > caller expected error pointers and one expected NULL pointers.  Change
> > it to return NULL and update the caller which expected error pointers,
> > drm_syncobj_assign_null_handle(), to check for NULL instead.
> >
> > Fixes: f781f661e8c9 ("dma-buf: keep the signaling time of merged fences v3")
> > Signed-off-by: Dan Carpenter <dan.carpenter at linaro.org>
>
Thanks for catching this!
> Reviewed-by: Christian König <christian.koenig at amd.com>
Reviewed-by: Sumit Semwal <sumit.semwal at linaro.org>
>
> Should I push that one to drm-misc-fixes?
If you haven't pushed already, I can push it now.
>
> Regards,
> Christian.

Best,
Sumit.
>
> > ---
> > v2: Fix it in dma_fence_allocate_private_stub() instead of
> >     __dma_fence_unwrap_merge().
> >
> >
> >   drivers/dma-buf/dma-fence.c   | 2 +-
> >   drivers/gpu/drm/drm_syncobj.c | 4 ++--
> >   2 files changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
> > index ad076f208760..8aa8f8cb7071 100644
> > --- a/drivers/dma-buf/dma-fence.c
> > +++ b/drivers/dma-buf/dma-fence.c
> > @@ -160,7 +160,7 @@ struct dma_fence *dma_fence_allocate_private_stub(ktime_t timestamp)
> >
> >       fence = kzalloc(sizeof(*fence), GFP_KERNEL);
> >       if (fence == NULL)
> > -             return ERR_PTR(-ENOMEM);
> > +             return NULL;
> >
> >       dma_fence_init(fence,
> >                      &dma_fence_stub_ops,
> > diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
> > index 04589a35eb09..e592c5da70ce 100644
> > --- a/drivers/gpu/drm/drm_syncobj.c
> > +++ b/drivers/gpu/drm/drm_syncobj.c
> > @@ -355,8 +355,8 @@ static int drm_syncobj_assign_null_handle(struct drm_syncobj *syncobj)
> >   {
> >       struct dma_fence *fence = dma_fence_allocate_private_stub(ktime_get());
> >
> > -     if (IS_ERR(fence))
> > -             return PTR_ERR(fence);
> > +     if (!fence)
> > +             return -ENOMEM;
> >
> >       drm_syncobj_replace_fence(syncobj, fence);
> >       dma_fence_put(fence);
>


-- 
Thanks and regards,

Sumit Semwal (he / him)
Tech Lead - LCG, Vertical Technologies
Linaro.org │ Open source software for ARM SoCs